High performance indoor light harvesters with a wide-gap donor polymer PBDB-T

Organic solar cells have received widespread attention with the development of indoor light harvesters. Due to the narrow emission spectra and weak light intensity of indoor emissions, the short-circuit current of indoor devices is largely restricted, and there would be an additional voltage loss around 0.15 V from the light intensity difference. However, most state-of-the-art cells cannot be adopted as indoor photovoltaics directly, because their small optical bandgaps lead to open-circuit voltage (V-OC) values in the range of similar to 0.6 V in dim-lighting, which is difficult to drive most of internet of things. Herein, we revaluate the photovoltaic performance under indoor illuminances by combining a wide-gap polymer PBDB-T with various electron-accepting materials. The PBDB-T: BTA3 cell achieves an excellent efficiency higher than 25% under a 1000 lux 2700K LED illumination. The V-OC value of such a device can still maintain close to 1 V under indoor cases. We then compare the underlying mechanism of the PBDB-T-based bulk heterojunctions (BHJs) with multiple techniques, and the results indicate the unchanged advantage of high V-OC helps the BTA3-based cell shows the best indoor device performance when the light source is switched from AM1.5G to low illumination. This work revaluates the selection of state-of-theart indoor light harvesters, and demonstrate an excellent optimal efficiency of the PBDB-T:BTA3 indoor cell up to 25.6%, with a desirable V-OC of 0.99 V.

Automated summary

Organic solar cells have attracted attention for indoor light harvesting, achieving high efficiency over 25% under 1000 lux 2700K LED illumination by combining a wide-gap polymer PBDB-T with various electron-accepting materials. The use of PBDB-T:BTA3 as an indoor cell shows optimal efficiency up to 25.6% with a desirable V-OC of 0.99 V.