Building mechanism for a high open-circuit voltage in an all-solution-processed tandem polymer solar cell

Kong

Advanced Energy Materials

et al. 2014

Self Cite

into the ITO electrode. [5][6][7][8] One of the promising ETLs is a class of materials known as solution-based metal oxide systems, such as titanium sub-oxide (TiO x ) and zinc oxide (ZnO). Because such metal oxides have specifi c energy levels to only transfer electrons, their operation as ETLs is compatible with their excellent electron-transporting and hole-blocking characteristics. [ 2,3,9,10 ] Numerous synthetic processes have been developed for those metal oxide systems. In particular, sol-gel synthesis of those metal oxide systems has received intense attention because of its simple solution process for uniform fi lm formation at room temperature (RT). When sol-gel processed TiO x (or ZnO) is coated between ITO and the BHJ layer, the layer acts as an ETL in i-PSCs by aligning energy levels and selecting only electron transport. However, because of the low carrier density or the many trap sites in the semiconducting metal oxide, a Schottky barrier develops at the high WF-metal/metal-oxide interface or energy level mismatching at the metal oxide/BHJ layer interface becomes a recurring issue. [9][10][11][12][13][14][15] Those problems hinder the electron transport between the BHJ layer and ITO and result in the extremely low device performance in i-PSCs, as shown in Figure 1 a. [9][10][11][12]14,15 ] Although photo-excitation of the metal oxides by UV-irradiation increases the carrier density in the metal oxides and recovers the device performance by narrowing and lowering the depletion barrier, as in Figure 1 b, through a so-called a "lightsoaking process," such a photoreduction process takes several minutes and the absence of UV light irradiation (for example, UV protection coating etc.) would be critical for practical applications. [9][10][11][12][13][14][15] Although many researchers have tried to fi nd a fundamental solution to remove the light-soaking process of the metal oxides in the i-PSCs, there has been no successful approach that is directly applicable to printable photovoltaics.The light-soaking process in i-PSCs with the TiO x ETL implies that the increased carrier density in TiO x by chemical doping can be a fundamental solution for this problem. In general, doping the titanium oxide system precedes the reduction process, for example nitrogen (N) doping of titanium dioxide (TiO 2 ). When titanium-oxygen (Ti-O) bonds are replaced with the titanium-nitrogen (Ti-N) bonds, it is well known that the carrier density of TiO 2-δ N δ substantially increases. [16][17][18][19] However, because the formation of the Ti-O bonds is a predominant process in the typical sol-gel method, it has been impossible to control the doping process in the sol-gel fabrication of the metal oxide systems. [ 18,[20][21][22] Such a diffi culty in the doping process often requires additional purifi cations of the sol-gel processed metal oxides, for example, washing or heating processes. [ 18,[21][22][23] Bulk heterojunction (BHJ) polymer solar cells (PSCs) continue to be a promising approach for low-cost energy harvesting becau...

Section: Doi: 101002/aenm201401298mentioning

confidence: 99%

Section: Photovoltaic Parameters Of Inverted Pscs (Ptb7‐th:pc70bm) Unmentioning

confidence: 99%

See 1 more Smart Citation

Overcoming the Light‐Soaking Problem in Inverted Polymer Solar Cells by Introducing a Heavily Doped Titanium Sub‐Oxide Functional Layer

Kong

Advanced Energy Materials

et al. 2014

Self Cite

“…poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/metal oxide is the most used ICL in tandem OSCs. The n-type metal oxide nanoparticles, such as zinc oxide (ZnO), [81,82,206] titanium dioxide (TiO 2 ), [33,140,154,207] and tin oxide (SnO 2 ), [77] are prepared by hydrothermal methods and dispersed in polar organic solvents. The surface defects of ZnO and aluminum-doped ZnO (AZO) can be modified by self-assembled monolayer (C 60 -SAM) with anchoring groups, [155] and polymer electrolytes of poly(9,9 0 -bis(6 00 -N,N,N-trimethylammoniumhexyl) fluorene-co-alt-phenylene) dibromide (FPQ-Br), [89] polyethylenimine (PEI), [69,115] partially ethoxylated polyethylenimine (PEIE), [108,138,164] etc.…”

Section: The Icls For Tandem Oscsmentioning

confidence: 99%

Recent Advances Toward Highly Efficient Tandem Organic Solar Cells

Peng

2020

Small Structures

Organic solar cells (OSCs) have attracted considerable attentions and have witnessed rapid progress from the aspects of material design, device engineering, and device physics. Tandem OSCs stacking more than one single-junction device in series or parallel connection are developed to diminish the thermalization and/ or transmission losses for improving the device performances. The optical managements by developing new photoactive materials, using high-conductive semitransparent interconnecting layers and smart device architectures are the key factors toward high-performance tandem OSCs. Herein, the recent advances in tandem OSCs are summarized from the aspects of photosensitive materials, interconnecting layers, and specific device structures. Finally, challenges and perspectives in the future development of tandem OSCs are also presented.

“…To broaden the light absorption range, a low-bandgap polymer was employed for the rear cell to absorb the residual light from the front cell 82 . Table 2 lists all of the high-efficiency, 5 to 10.6 %, multi-junction polymer:fullerene solar cells that include conventional and inverted device structures 1, 18,[83][84][85][86][87][88][89][90] . An efficiency of 10.6 %, the highest PCE, for a multi-junction OPV that was developed by UCLA and Sumitomo Chemical Corporation jointly has been posted on the NREL website without detailing its active layer or device structures.…”

Section: Conclusion and Future Prospectsmentioning

confidence: 99%

Organic photovoltaics

Demming¹,

Krebs

Chen

2013

Nanotechnology

Organic photovoltaics In the last ten years, the highest efficiency obtained from organic photovoltaics (OPVs), such as bulk heterojunction polymer:fullerene solar cells, has risen from 2.5 to 11 %. This rapid progress suggests that the commercialization of OPVs should be realized soon if we can solve some technical issues. The advances in the development of OPVs can be attributed to four fronts: (i) a better understanding of the mechanism of photon-to-electron conversion; (ii) new materials with tailored energy levels and solubility; (iii) new processing approaches to induce optimal microstructures in the active layer; and (iv) new device architectures with novel interfacial layers. Herein, we review the materials, the microstructures of the active layers, the device structures, the interfacial layers that have been developed recently for OPVs, and provide future perspectives for this promising technology.