We have studied the effect of buffer layers on the performance of poly(3-hexylthiophene-2,5-diy1) (P3HT):C61-butyric
acid methyl ester (PCBM) bulk heterojunction solar cells. We proved that depositing a thin pentacene layer between
metal cathode and P3HT: PCBM blend and introducing a thin P3HT layer between ITO and photoactive layer, would
improve the power conversion efficiency of polymer bulk heterojunction solar cells when compared with the cells
without the buffer layers. In the study, the buffer layers increased short circuit density (Jsc) and open circuit voltage
(Voc) under the illumination by white light from a solar simulator with an incident intensity of 100mW/cm2. The thin
pentacene layer as a cathode buffer layer modifying the contact between the active layer and the cathode, the thin layer
of P3HT as a anode buffer layer enhancing the electron blocking ability were responsible for the improvement on the
performance of photovoltaic device.
Investigating the effects of solvents on the performance of poly(3-hexylthiophene-2,5-diy1) (P3HT):C61-butyric acid
methyl ester (PCBM) bulk heterojunction solar cells, we found the short current density (Jsc), fill factor(FF),and power
conversion efficiency (η) of a cell with a photo-active layer made using materials dissolved in a higher boiling point
solvent to be higher than those of a cell made using the same materials dissolved in a low boiling point solvent.
Evaluating the surface morphology, charge mobility, and current-voltage curve of cells made using different solvents, we
concluded that the polymer films using a higher boiling point solvent had longtime to self-organize, got a higher degree
of crystalline, led to lower device series resistance, thereby increased the short current density (Jsc), fill factor(FF),and
power conversion efficiency (η) of the photovoltaic devices.
The effect of interlayer on the performance of a poly[2-methoxy-5-(3',7'-dimethylocty)-1,4-phenylenevinylene]
(MDMO-PPV)/1-(3-methoxycarbony 1)-propy1-1 phney1-(6-6)C<sub>61</sub> (PCBM) composite solar cell device has been
reported recently. Herein we report bulk heterojunction organic solar cell with efficiency enhanced by interlayer made
from blend film of regioregular poly(3-hexylthiophene)(P3HT) and PCBM. The interlayer, poly(9,9-dioctylfluorene)-<i>co</i>-<i>N</i>-(1,4-butylphenyl)diphenylamine)(TFB), was inserted between the poly(3,4-ethylene dioxythiophene)-poly(styrene
sulfonic acid)(PEDOT:PPS) and the active layer. With the interlayer, the efficiency was enhanced due to the increased
short circuit current density (<i>J</i>sc), open circuit voltage (<i>V</i>oc) and fill factor (FF) obtained from testing and calculation.
According to the analysis, the interlayer TFB, acting as an effective exciton-blocking layer, prevented the severe
quenching of radiative excitons between the interface of PEDOT:PSS. In the study, the interlayer increased <i>J</i>sc from
0.891 mA/cm<sup>2</sup> to 1.025 mA/cm<sup>-2</sup>, <i>V</i>oc from 0.478 V to 0.526 V, and FF from 0.327 to 0.416, under illumination by
white light from a solar simulator with an incident intensity of 80mW/cm<sup>2</sup>; the power conversion efficiency of the
device reached higher value 0.280% comparing with 0.174% with no interlayer.