Efficient and highly light stable planar perovskite solar cells with graphene quantum dots doped PCBM electron transport layer

Organic-inorganic hybrid perovskite solar cells (PSCs) have triggered a great deal of research on organic electron transport layers, such as phenyl C61 butyric acid methyl ester (PCBM), due to their potential application as a strong contender in photovoltaic industry with simple fabrication process and low cost. However, the low electrical conductivity and electron mobility of PCBM hinder the promotion of PSCs. Here we report a successful case of graphene quantum dots (GQDs) doping into PCBM electron transport layer (ETL) of planar N-I-P PSCs, resulting in an obvious increase in PCBM conductivity together with the enhanced charge extraction and reduced the trap state density of perovskite films. A low doping ratio (0.5 wt%) would be efficient to boost the Voc, Jsc and FF, a PCE of 17.56% is achieved. More importantly, the light stability of PSCs with PCBM: GQDs was improved: the unpackaged cells can keep > 80% of the initial PCE under simulated sunlight with the full UV component present after 300 h, in contrast to the reference device that dropped < 50% during the same period of time.