Abstract:
P3HT:PCBM bulk heterojunction solar cells with poly 3,4-
ethylenedioxythiophene:poly styrenesulfonate (PEDOT: PSS) as Hole
Blocking Layer (HBL) has become increasingly feasible with large-area of
donor–acceptor interface for efficient light-induced charge separation. Few
metal oxides have also been utilized for P3HT: PCBM based solar cells as
HBL which blocks the back electron leakage and increasing the charge
collection before recombining. Although PEDOT: PSS has been heavily
studied in these types of solar cells, it has been identified as a source for
degrading the active layer due to its hydrophobic nature. In this study,
inverted P3HT: PCBM solar cells were fabricated by using either of CdS and
TiO2 thin films as HBL, and the effects of CdS layer thickness on the device
performance were investigated. The device with thin CdS layer offered short
circuit (JSC) over 7.5 mA/cm2with an open circuit voltage (VOC) of 0.57 V
which provides overall power conversion efficiency of over 2 % under AM
1.5 illumination (100 mW/cm2
) conditions, which is over 100 % higher than
that of Titanium dioxide thin film as the hole blocking layer. The major
contribution is 75 % improvement in the VOC, due to the lower work function
of CdS. Even though there was a small improvement in the VOC with the
thickness of CdS thin film, the conversion efficiency is decreased due to
reduced JSC as per the strong absorption of CdS in the UV region verified by
the optical absorption spectra.
