Grain boundary passivation with sulfonated graphene to enhance perovskite photodetector performance

Organic-inorganic hybrid perovskite films possess superior optoelectronic properties, including bandgap tunability, high absorption coefficient, well-balanced charge carrier mobility and long electron-hole diffusion length. Hence it can serve as sensitizers in solar cells, photodetectors, pumped lasers and light-emitting diodes. However, the crystallographic defect passivation and suppression of organic-inorganic hybrid perovskite at the grain boundaries are crucial for efficient and stable perovskite photodetectors (PPDs). Herein, a bulk heterojunction (BHJ) fabricated by the two-step spin-coating method facilitates high-quality perovskite film formation while reducing the non-radiative recombination within the photoactive layer, enhancing the photosensitivity performance of PPDs based on BHJ configuration. Specifically, sulfonated graphene (SGA) was used as a functional passivator to interact with Pb2+ at the surface and grain boundaries due to its large specific surface area and high binding energy with lead ion, thereby ameliorating the device stability and carrier transport capacity within perovskite films, resulting in a lower dark current density and a higher photocurrent density. Consequently, the PPD based on the BHJ configuration achieves a responsivity of 570 mA/W and the specific detectability of 6.3×1011 Jones under the bias voltage of −1 V with the 532 nm laser illumination intensity of 0.5 μW/cm2 and a linear dynamic range of 126 dB. The PPD based on BHJ configuration shows ultrahigh response rates of 0.3 μs and 52.7 μs for the rise and fall times at zero bias, respectively, which is attributed to efficient carrier extraction and the lower defect density. The grain boundary passivation strategy of SGA modification develops a practical approach to ameliorate PPD performance and stability.