Fig. 5. (a) ESR signals of the RR-P3HT/PCBM composite MIS diode measured with microwave power of 0.02mW at 10 K. Solid and dashed curves show ESR signals obtained at VG = +10 and 0V, respectively. (b) Field-induced ESR signal due to the PCBM radical anions, obtained by subtracting ESR signal at VG = 0V from that at VG = +10 and +30 V.