Power conversion efficiency (PCE), lifetime and cost are critical factors to practical applications of photovoltaic cells. With the advent of the Internet of Things, vast amounts of off-grid energy sources are needed to drive low-power-consumption products for indoor applications. However, the mature c-Si cells can't meet the application needs because their PCEs are only 2-6% under the indoor illumination conditions mainly due to the mismatch of absorption spectrum and severe charge recombination at low carrier density. Therefore, it is urgent to develop new photovoltaic cells for indoor applications.
Recently, the research team led by Prof. HOU Jianhui at Institute of Chemistry, Chinese Academy of Sciences (ICCAS) and Prof. GAO Feng at Link？ping University in Sweden, developed an organic photovoltaic (OPV) cell with outstanding efficiency under the indoor light conditions. By blending polymer donor named PBDB-TF and a carefully designed acceptor named IO-4Cl, they made a photoactive layer with an absorption spectrum matching with the indoor illumination sources. The 1 cm² OPV cell achieved a PCE of 26.1% with an open-circuit voltage of 1.10V under the illumination of 1000 lux (2700 K). Impressively, this work demonstrates this OPV cell not only has high PCE and excellent stability but also can be made in large area. For example, the OPV cell almost maintained its initial PCE under continuous illumination after 1000 hours, and a 4cm² cell prepared via a blade-coating method can realize a PCE of over 23%.
The study entitled “Wide-gap non-fullerene acceptor enabling high-performance organic photovoltaic cells for indoor applications” was published in Nat. Energy, 2019, 4, 768.
This work was financially supported by National Natural Science Foundation of China, Beijing National Laboratory for Molecular Sciences, Chinese Academy of Sciences, Swedish Research Council VR, the Swedish Energy Agency Energimyndigheten and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Link？ping University.

Figure (a) The critical indicators for the practical applications. (b) The normalized emission power spectrum of light sources. (c) Normalized absorption spectra of PBDB-TF and IO-4Cl as films. (d) The curves of the photovoltaic characteristics versus time. (e) The J–V curves of a 4 cm² cell based on a blade-coating method under AM 1.5G and an LED. (f) Efficiency prediction of the OPV cells (LED, 2700K). (Image by Prof. HOU Jianhui)

Contact:
Prof. HOU Jianhui
Institute of Chemistry, Chinese Academy of Sciences
Beijing, 100190, China
Tel: 010-82615900
Email: hjhzlz@iccas.ac.cn