High-performance Organic Photodetector Based On SnO₂ Modified Layer

In organic or organic-inorganic hybrid perovskite-type photovoltaic devices,metal oxide semiconductor thin films?Ti O₂,SnO₂,Zn O,etc.?are often used as a modification layer to improve device performance,and how to reduce the surface defects of metal oxides often plays a crucial role in improving the performance of solar cell devices.Therefore,the removal of interfacial defects through high-temperature thermal annealing and ultraviolet ozone treatment has been widely used and studied in solar cell devices.However,unlike solar cells,photomultiplier photodetectors can trap charges by introducing interface defects and reduce dark current.At the same time,the accumulation of photo-generated charges caused by defects can cause tunneling currents and eventually form high gains.However,studies on the effects of high-temperature thermal annealing and ultraviolet ozone treatment to remove interface defects on the performance of photodetectors are rarely reported.SnO₂ has attracted more and more attention as it is widely used in high-efficiency perovskite solar cells,but there are few reports on the research of polymer photodetectors.In this work,SnO₂ was introduced into P3HT polymer heterojunction photodetector,which significantly improves the performance of the device.At the same time,the research on the influence of SnO₂ nanoparticle defects on the detector performance was carried out.The main content includes three parts.1.The untreated SnO₂ film at room temperature was used as an interlayer between the ITO electrode and the photoactive layer.The SnO₂ film was not processed in any way and was very suitable for optoelectronics with a processing temperature below 150?.The untreated SnO₂ film introduced defects and suppressed the dark current of the device.In the light state,external charge tunneling was injected to form a high gain.The signal-to-noise ratio exceeded 5×10⁵ at-1 V bias,and the highest external quantum efficiency reached 1430%.The specific detection rate reached 2.24×10¹³ Jones.By changing the ratio of the acceptor to the electron transmission channel inside the active layer,the dark current was further reduced to 0.14 n A cm^-2.Because the electronic transmission was restricted,the device only had an optical response to a specific wavelength band.2.Different treatment methods can significantly change the number of the SnO₂surface defects,and the defects will change the work function and conductivity of SnO₂.For the untreated SnO₂ devices at room temperature,the defects increased the injection barrier between the ITO electrode and the SnO₂ film,leading to a reduced dark current;in the light state,photo-generated electrons filled the surface defect states of SnO₂,and the SnO₂ conductivity recovered and decreased the injection barrier at the electrode interface.In addition,the tapped carriers by the defects caused the energy band bend at the active layer surface,resulting in a dramatically enhanced electron injection into the device from the ITO electrode,and thus forming a high gain.3.High-temperature treatment of the SnO₂ modified layer not only affected the SnO₂layer but also changed the characteristics of the ITO film.Under high-temperature treatment,the number of the SnO₂ surface defects became less,and the ITO work function increased.The increased charge injection barrier of the device caused a decreased dark current.In the device without any modification layer,that high-temperature annealing of ITO can change the ITO conductivity and transmittance while the photocurrent of the device almost has no change.The decreased dark current made the performance of the device comparable to that of the device with an electron-blocking layer at-0.5 V,the dark current density was only 7.3×10^-5 m A cm^-2,the signal-to-noise ratio reached 1.5×10⁵,the specific detection rate exceeded 10¹² Jones,and the rise time of the device was only6?s.