Silver-indium-sulfide quantum dots in titanium dioxide as electron transport layer for highly efficient and stable perovskite solar cells

Silver-indium-sulfide (AgInS2) quantum dots in TiO2 was prepared to use as an electron transport layer of planar perovskite solar cell (PSC). The average value of the root mean square of the surface roughness of the electron transport layer was slightly reduced by the addition of AgInS2 into TiO2. The electron mobility of the electron transport layer was enhanced from 1.34x10(-5) to 2.05x10(-5)cm(2)V(-1)s(-1) after the addition of AgInS2. The external quantum efficiency (EQE) of the device with TiO2:AgInS2 was improved in the region from 300 to 750nm as compared with that of the device without AgInS2. This result was separately caused by following two factors: one was the efficient light harvesting by AgInS2 in the region from 300 to 450nm, and another was the improvement of the charge transfer from perovskite layer to TiO2 through AgInS2 in the region from 450 to 750nm. Over 15% enhancement of the power conversion efficiency (PCE) of the PSC was achieved by the addition of 0.8mgmL(-1) of AgInS2 into TiO2. Storage of the PSCs with or without AgInS2 with encapsulation in air resulted in long stability for 200days in terms of the PCEs, which were kept relatively 111% and 92% as compared with the initial values, respectively. Addition of AgInS2 into TiO2 brought the improvement of the durability against the photodegradation.