In this work, we report efficient semitransparent perovskite solar cells using solution-processed silver nanowires (AgNWs) as top electrodes. A thin layer of zinc oxide nanoparticles is introduced beneath the AgNWs, which fulfills two essential functionalities: it ensures ohmic contact between the PC 60 BM and the AgNWs and it serves as a physical foundation that enables the solution-deposition of AgNWs without causing damage to the underlying perovskite. The as-fabricated semitransparent perovskite cells show a high fill factor of 66.8%, V oc = 0.964 V, J sc = 13.18 mA cm −2 , yielding an overall efficiency of 8.49% which corresponds to 80% of the reference devices with reflective opaque electrodes.Inorganic-organic halide perovskite solar cells have recently emerged as a promising photovoltaic technology due to their high efficiencies and low-cost processing potential. [1][2][3][4] The exceptional optoelectronic properties of the perovskite crystals such as high carrier mobility and long charge diffusion length promise highly efficient charge separation. 5,6 These intriguing characteristics make perovskites ideal materials for photovoltaic applications. Since the first device demonstration in 2009, power conversion efficiency (PCE) of perovskite solar cells processed by both vacuum-deposition and solutionprocessing has surged to over 15%. 2,4,[7][8][9] The continuous and fast progress in the research related to perovskite solar devices has established them as a serious contestant to the traditional silicon-based panels.Together with the considerable efforts devoted to pursuing high efficiencies via improved crystallization of perovskite and searching for low-cost interface materials, 4,10-13 aesthetic semitransparent perovskite solar cells have been simultaneously receiving growing attention because of their specific application in transparent architectures, 14-17 such as windows, rooftops, greenhouses and other fashion elements. To achieve efficient semitransparent perovskite devices, both the anode and the cathode of the devices should be highly transparent and conductive in order to minimize the optical and resistance losses. To date, several studies have reported semitransparent perovskite solar cells, but most of these devices employed thin metal films (Al, Ag, Au) as top electrodes which were fabricated based on energy-intensive evaporation processes. [15][16][17] It is well known that, in addition to low-cost materials, the cost reduction of photovoltaic devices substantially depends on the ability to use high-throughput coating techniques in combination with roll-to-roll processing. 18 Despite its importance, however, less attention has been paid to the exploration of solution-processable transparent electrodes for perovskite solar cells. Carbon based materials have received much attention for use as conducting electrodes for perovskite solar cells, due to their low-cost and high stability. 14,19,20 For example, Li et al.have recently reported semitransparent perovskite solar cells using carbon nanotub...

Perovskite hybrid solar cells (pero-HSCs) were demonstrated to be amongst the most promising candidates within the emerging photovoltaic materials with respect to their power conversion efficiency (PCE) and inexpensive fabrication. Further PCE enhancement mainly relies on minimizing the interface losses via interface engineering and the quality of the perovskite film. Here we demonstrate that the PCEs of pero-HSCs is significantly increased to 14.0% by incorporation of a solution-processed perylene diimide (PDINO) as cathode interface layer between [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) layer and the top Ag electrode. Notably, for PDINO based devices, prominent PCEs over 13% are achieved within a wide range of the PDINO thickness (5-24 nm). Without the PDINO layer, the best PCE of the reference PCBM/Ag device was only 10.0%. The PCBM/PDINO/Ag devices also outperformed the PCBM/ZnO/Ag devices (11.3%) with the well-established zinc oxide (ZnO) cathode interface layer. This enhanced performance is due to the formation of a highly qualitative contact between PDINO and the top Ag electrode, leading to reduced series resistance (R s ) and enhanced shunt resistance (R sh ) values. This study opens the door for the integration of a new class of easy-accessible, solution-processed high performance interfacial materials for pero-HSCs.

One of the biggest challenges for the commercialization of polymer‐based and other printed photovoltaic (PV) technologies is to establish reliable up‐scaling processes that minimize the efficiency losses occurring during the transition from record laboratory cells to roll‐to‐roll (R2R) printed PV modules. This article reviews the latest advances in reducing the efficiency gap between record solar cells and large‐area organic PV modules. The major loss sources are identified for the most popular cell architectures and categorized into optical, electrical, and processing‐related contributions. Their relative shares in the overall efficiency drop are quantified through optical and electrical simulations. Further potential sources of efficiency loss, such as the replacement of halogenated by green solvents for active layer processing, are also addressed. Finally, the effect of reduced efficiency gaps on the production costs of R2R printed modules is discussed, demonstrating that values as low as € 0.5 Wp−1 (the nominal power of a solar module/cell) can be achieved.

While perovskite-based semitransparent solar cells for window applications show competitive levels of transparency and efficiency compared to organic photovoltaics, the color perception of the perovskite films is highly restricted because band gap engineering results in losses in power conversion efficiencies. To overcome the limitation in visual aesthetics, we combined semitransparent perovskite solar cells with dielectric mirrors. This approach enables one to tailor the device appearance to almost any desired color and simultaneously offers additional light harvesting for the solar cell. In the present work, opto-electrical effects are investigated through quantum efficiency and UV-to-visible spectroscopic measurements. Likewise, a detailed chromaticity analysis, featuring the transmissive and reflective color perception of the device including the mirror, from both sides and in different illumination conditions, is presented and analyzed. Photocurrent density enhancement of up to 21% along with overall device transparency values of up to 31% (4.2% efficiency) is demonstrated for cells showing a colored aesthetic appeal. Finally, a series of simulations emulating the device chromaticity, transparency, and increased photocurrent density as a function of the photoactive layer thickness and the design wavelength of the dielectric mirror are presented. Our simulations and their experimental validation enabled us to establish the design rules that consider the color efficiency/transparency interplay for real applications.

Graphene grown on Rh(111) was used as a template for the growth of Pd nanoclusters. Using high-resolution synchrotron radiation-based X-ray photoelectron spectroscopy, we studied the deposition of Pd on corrugated graphene in situ. From the XP spectra, we deduce a cluster-by-cluster growth mode. The formation of clusters with 3 nm diameter was confirmed by low-temperature scanning tunneling microscopy measurements. The investigation of the thermal stability of the Pd particles showed three characteristic temperature regimes: Up to 550 K restructuring of the particles takes place, between 550 and 750 K the clusters coalesce into larger agglomerates, and finally between 750 and 900 K Pd intercalates between the graphene layer and the Rh surface.

Nanocluster arrays on graphene (Gr) are intriguing model systems for catalysis. We studied the adsorption and oxidation of CO on Pt/Gr/Rh(111) with synchrotron-based high-resolution X-ray photoelectron spectroscopy. On the nanoclusters, CO is found to adsorb at three different sites: namely, on-top, bridge, and step. The C 1s spectra exhibit remarkable similarities to those on the stepped Pt(355) surface. Similar to the case for stepped Pt surfaces, a clear preference for the adsorption on the step sites is found, while the preference for the adsorption on the on-top site over the bridge site on the terraces is much less pronounced in comparison to that on Pt single crystals. Temperatureprogrammed X-ray photoelectron spectroscopy revealed an enhanced binding energy for the cluster step sites, similar to the situation on stepped Pt surfaces. The oxidation of CO on graphene-supported Pt nanoclusters follows a pseudo-first-order rate law. Applying an Arrhenius analysis, we found an activation energy of 13 ± 4 kJ/mol, which is much smaller than that on Pt(111), due to the more reactive step and kink sites on the nanoclusters.

Semitransparent solar cells (SSCs) can open photovoltaic applications in many commercial areas, such as power‐generating windows and building integrated photovoltaics. This study successfully demonstrates solution‐processed small molecule SSCs with a conventional configuration for the presently tested material systems, namely BDTT‐S‐TR:PC70BM, N(Ph‐2T‐DCN‐Et)3:PC70BM, SMPV1:PC70BM, and UU07:PC60BM. The top transparent cathode coated through solution processes employs a highly transparent silver nanowire as electrode together with a combination interface bilayer of zinc oxide nanoparticles (ZnO) and a perylene diimide derivative (PDINO). This ZnO/PDINO bilayer not only serves as an effective cathode buffer layer but also acts as a protective film on top of the active layer. With this integrated contribution, this study achieves a power conversion efficiency (PCE) of 3.62% for fully solution‐processed SSCs based on BDTT‐S‐TR system. Furthermore, the other three systems with various colors exhibited the PCEs close to 3% as expected from simulations, demonstrate the practicality and versatility of this printed semitransparent device architecture for small mole­cule systems. This work amplifies the potential of small molecule solar cells for window integration.

While perovskite-based semitransparent solar cells deliver competitive levels of transparency and efficiency to be envisioned for urban infrastructures, the complexity and sensitivity of their processing conditions remain challenging. Here, we introduce two robust protocols for the processing of sub-100 nm perovskite films, allowing fine-tuning of the active layer without compromising the crystallinity and quality of the semiconductor. Specifically, we demonstrate that a method based on solvent-induced crystallization with a rapid drying step affords perovskite solar cells with 37% average visible transmittance (AVT) and 7.8% PCE. This process enhances crystallization with a preferential phase orientation presumably at the interface, yielding a high fill factor of 72.3%. The second method is based on a solvent-solvent extraction protocol, enabling active layer films as thin as 40 nm and featuring room-temperature crystallization in an ambient environment on a few second time span. As a result, we demonstrate a maximum AVT of 46% with an efficiency of 3.6%, which is the highest combination of efficiency and transparency for a full device stack to date. By combining the two methods presented here we cover a broad range of thicknesses vs. transparency values and confirm that solvent-induced crystallization represents a powerful processing strategy toward high-efficiency semitransparent solar cells. Optical simulations support our experimental findings and provide a global perspective of the opportunities and limitations of semitransparent perovskite photovoltaic devices.