Investigation of photocurrent and recombination dynamics of photodiodes based on polymeric materials

Organic photodiodes (OPD) based on P3HT: PCBM bulk heterojunction were fabricated and characterized under different voltage bias. The photodiodes demonstrated a stable signal around specified wavelength at 550 nm under a reverse bias at -2.5V, showing a potential application for specific wavelengths detection. The photocurrent responsivity indicated that free charge carriers can be extracted within microseconds after the light cut-off. The periodic time was about 2 mu s (fastest was 1.5 ps under high intensity condition) under different light intensity. The transient technique was applied to investigate the recombination rate inside of organic photodetector in order to elucidate the dominant decay mechanism. The mobility and charge carrier density values obtained with transient absorption spectrum show a result of geminate recombination after exciton separation being the dominant loss mechanism. Although the process was dominated by recombination, OPD worked perfectly in low light condition indicating a potential application in sensing market.