Realization of high performance for PM6:Y6 based organic photovoltaic cells

With advances in material science and a more in-depth understanding of device engineering,the power conversion efficiency(PCE)of solution-processed organic photovoltaic(OPV)cells have significantly boosted in the past few years.In 2019,a high PCE of 15.7%was achieved in the OPV cells adopting a wide bandgap polymer PM6 and a new emerging non-fullerene acceptor Y6.Such outstanding performance has attracted lots of research attention,driving considerable efforts to improve or take advantage of the high-performance PM6:Y6-based system.In this review,we first concentrate on the structural characteristics of PM6 and Y6 with the focus on understanding why their combination for OPV application can obtain such high efficiency.We also update the recent progress in highly efficient PM6:Y6-based OPV cells via various optimizing strategies.Then we summarize the other applications of the PM6:Y6-based system in semi-transparent,flexible or lay e-by-layer devices.The prospects for future OPV studies will be suggested in the end.

Printable SnO2 cathode interlayer with up to 500 nm thickness-tolerance for high-performance and large-area organic solar cells

The printable electrode interlayer with excellent thickness tolerance is crucial for mass production of organic solar cells(OSCs)by solution-based print techniques. Herein, high-quality printable SnO2 films are simply fabricated by spin-coating or bladecoating the chemical precipitated SnO2 colloid precursor with post thermal annealing treatment. The SnO2 films possess outstanding optical and electrical properties, especially extreme thickness-insensitivity. The interfacial electron trap density of SnO2 cathode interlayers(CILs) are very low and show negligible increase as the thicknesses increase from 10 to 160 nm,resulting in slight change of the power conversion efficiencies(PCEs) of the PM6:Y6 based OSCs from 16.10% to 13.07%. For blade-coated SnO2 CIL, the PCE remains high up to 12.08% even the thickness of SnO2 CIL is high up to 530 nm. More strikingly, the large-area OSCs of 100 mm2 with printed SnO2 CILs obtain a high efficiency of 12.74%. To the best of our knowledge, this work presents the first example for the high-performance and large-area OSCs with the thickness-insensitive SnO2 CIL.

Layer-by-layered organic solar cells:Morphology optimizing strategies and processing techniques

The last decades have witnessed the rapid development and the gradually improved efficiencies of organic solar cells(OSCs),which show great potentials in the fabrication of eco-friendly and flexible photovoltaic panels.Layer-by-layered(LBL)structure via sequential processing of the donor and acceptor layers becomes an advisable option to construct pseudo-bilayer configurations in OSC active layer.Favorable vertical phase separation and sufficient exciton dissociation interfaces can be simultaneously realized in such aggregation morphology via different processing technologies and strategies.High efficiencies of over 18%in ternary LBL device and 11.9%in LBL-processed module(11.52 cm2)have been successfully achieved in recent works.Moreover,the unique merits of LBL structure in individual layer processing enable it a promising candidate for large-scale printing and further industrialization of OSCs.This perspective provides the recent advance of LBL OSCs with the focus on fabrication technologies and strategies for morphology control and also proposes the current thinking and perspective on LBL structures for future development.

Efficient organic solar cells with low-temperature in situ prepared Ga_(2)O_(3) or In_(2)O_(3) electron collection layers

Facile synthesis of an interfacial layer in organic solar cells (OSCs) is important for broadening material designs and upscaling photovoltaic conversion efficiency (PCE).Herein,a mild solution process of spin-coating In(acac)3and Ga(acac)3isopropanol precursors followed by low-temperature thermal treatment was developed to fabricate In_(2)O_(3)and Ga2O3cathode buffer layers (CBLs).The introduction of In_(2)O_(3)or Ga2O3CBLs endows PM6:Y6-based OSCs with outstanding performance and high PCEs of 16.17%and 16.01%,respectively.Comparison studies present that the In_(2)O_(3)layer possesses a work function (WF) of 4.58 eV,which is more favorable for the formation of ohmic contact compared with the Ga2O3layer with a WF of 5.06 eV and leads to a higher open circuit voltage for the former devices.Electrochemical impedance spectroscopy was performed to reveal how In_(2)O_(3)and Ga2O3affect the internal charge transfer and the origin of their performance difference.Although In_(2)O_(3)possesses lower series resistance loss,Ga2O3has a higher recombination resistance,which enhances the device fill factor and compensates for its series resistance loss to some extent.Comparative analysis of the photo-physics of In_(2)O_(3)and Ga2O3suggests that both are excellent CBLs for highly efficient OSCs.

Size-Controllable Metal Chelates as Both Light Scattering Centers and Electron Collection Layer for High-Performance Polymer Solar Cells

An electron collection layer(ECL)between a photoactive overlay and an electrode plays a crucial role in optimizing the light field and charge extraction in bulk-heterojunction(BHJ)polymer solar cells(PSCs).However,the typical thickness of the photoactive layer is thinner than its optical path lengths,limiting further improvement of light absorption and device performance.