Following pioneering work, solution-processable organic-inorganic hybrid perovskites-such as CH3NH3PbX3 (X = Cl, Br, I)-have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixture of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled precipitation of the perovskite produces large morphological variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from solution into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a solution of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphology than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approximately 15 per cent (measured under standard AM1.5G test conditions on solar zenith angle, solar light intensity and cell temperature). This two-step method should provide new opportunities for the fabrication of solution-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today's best thin-film photovoltaic devices.

Dye-sensitized solar cells have gained widespread attention in recent years because of their low production costs, ease of fabrication and tunable optical properties, such as colour and transparency. Here, we report a molecularly engineered porphyrin dye, coded SM315, which features the prototypical structure of a donor-π-bridge-acceptor and both maximizes electrolyte compatibility and improves light-harvesting properties. Linear-response, time-dependent density functional theory was used to investigate the perturbations in the electronic structure that lead to improved light harvesting. Using SM315 with the cobalt(II/III) redox shuttle resulted in dye-sensitized solar cells that exhibit a high open-circuit voltage VOC of 0.91 V, short-circuit current density JSC of 18.1 mA cm(-2), fill factor of 0.78 and a power conversion efficiency of 13%.

Researchers developed a perovskite solar cell with high power-conversion efficiency (>20%) and intense electroluminescence yield (0.5%).

ABSTRACT:We report for the first time on a hole conductor-free mesoscopic lead iodide CH3NH3PbI3(perovskite)/TiO2 heterojunction solar cell, produced by deposition of perovskite nanoparticles from a solution of CH3NH3I and PbI2 in -butyrolactone on a 400nm thick film of TiO2 (anatase) nanosheets exposing (001) facets. An Au film was evaporated on top of the CH3NH3PbI3 served as a back contact. Importantly, the CH3NH3PbI3 nanoparticles act assumes here simultaneously the role of light harvester and hole conductor rendering superfluous the use of an additional hole transporting material. The simple mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cell shows impressive photovoltaic performance with short circuit photocurrent (Jsc) of 16.1 mA/cm 2 , an open circuit photovoltage (Voc) of 0.631 V and a fill factor (FF) of 0.57, corresponding to a light to electric power conversion efficiency (PCE) of 5.5% under standard AM 1.5 solar light of 1000 W/m 2 intensity. At a lower light intensity of 100W/m 2 a PCE of 7.3 % was measured. The advent of such simple solution processed mesoscopic heterojunction solar cells paves the way for new advances to realize low cost, high-efficiency solar cells.

This review presents the state-of-the-art organohalide lead perovskites, which are currently making an immense impact across the photovoltaic community.

Organic-inorganic hybrid perovskites have attracted attention as successful light harvesting materials for mesoscopic solid-state solar cells and led to record breaking effi ciencies. The photovoltaic performance of these devices is greatly dependent on the fi lm morphology, which in turn is dependent on the deposition techniques and subsequent treatments employed. In this work the perovskite fi lm is deposited by spin-coating a precursor solution of PbCl 2 and CH 3 NH 3 I (1 to 3 molar ratio) in dimethylformamide. Here, the role of the temperature used in the annealing process required to convert the as deposited solution into the perovskite material is investigated. It is found that the conversion requires suffi ciently high temperatures to ensure the vaporization of solvent and the crystallization of the perovskite material. However, increasing the annealing temperature too high leads to the additional formation of PbI 2 , which is detrimental to the photovoltaic performance. Furthermore, the effect of the annealing temperature on the fi lm formation, morphology, and composition is examined and correlated with the photovoltaic performance and device working mechanisms.

Hybrid organic-inorganic lead halide perovskite APbX3 pigments, such as methylammonium lead iodide, have recently emerged as excellent light harvesters in solid-state mesoscopic solar cells. An important target for the further improvement of the performance of perovskite-based photovoltaics is to extend their optical-absorption onset further into the red to enhance solar-light harvesting. Herein, we show that this goal can be reached by using a mixture of formamidinium (HN=CHNH3 (+), FA) and methylammonium (CH3 NH3 (+), MA) cations in the A position of the APbI3 perovskite structure. This combination leads to an enhanced short-circuit current and thus superior devices to those based on only CH3 NH3 (+). This concept has not been applied previously in perovskite-based solar cells. It shows great potential as a versatile tool to tune the structural, electrical, and optoelectronic properties of the light-harvesting materials.

Perovskite-based optoelectronic devices have gained significant attention due to their remarkable performance and low processing cost, particularly for solar cells. However, for perovskite light-emitting diodes (LEDs), non-radiative charge carrier recombination has limited electroluminescence (EL) efficiency. Here we demonstrate perovskite-polymer bulk heterostructure LEDs exhibiting record-high external quantum efficiencies (EQEs) exceeding 20%, and an EL half-life of 46 hours under continuous operation. This performance is achieved with an emissive layer comprising quasi-2D and 3D perovskites and an insulating polymer. Transient optical spectroscopy reveals that photogenerated excitations at the quasi-2D perovskite component migrate to lower-energy sites within 1 ps. The dominant component of the photoluminescence (PL) is primarily bimolecular and is characteristic of the 3D regions. From PL quantum efficiency and transient kinetics of the emissive layer with/without charge-transport contacts, we find non-radiative recombination pathways to be effectively eliminated. Light outcoupling from planar LEDs, as used in OLED displays, generally limits EQE to 20-30%, and we model our reported EL efficiency of over 20% in the forward direction to indicate the internal quantum efficiency (IQE) to be close to 100%. Together with the low drive voltages needed to achieve useful photon fluxes (2-3 V for 0.1-1 mA cm -2 ), these results establish that perovskite-based LEDs have significant potential for light-emission applications.