The Fabrication And Investigation Of Organic Solar Cells Based On Polymers

Organic solar cells based on polymers have advantages of wide material sources, low cost of fabrication, light weight, simple manufacturing processes, easily to produce in large quantities et al, which show great application potential and become one of hot issues of organic photovoltaic devices.The photovoltaic properties of organic solar cells based on polymers have been investigated in this article. Novel small molecular and polymers with narrow band gap were chosen to extend the absorption active range of sunlight; microwave annealing method was used to enhance the crystal characteristics and conductivity of materials; CNT material was used as anode to improve the input and transport abilities for holes. The works are listed as following:1. Bulk hetero-junction solar cells based on one novel fluorine-born compound (PIDB) and MEH-PPV have been fabricated. The results showed that the doping of PIDB made the absorption spectra of the MEH-PPV extended to about 30nm in visible range; the photovoltaic parameters of cells showed obvious changes along with the doping ratio of PIDB. The performance of cells achieved the best one when the ratio of the MEH-PPV and PIDB was 1:1 in weight; open circuit voltage(Voc) was 0.59V, fill factor(FF) was 0.54, and the power conversation efficiency (η) achieved to 0.31%. The reason of fill factor with large difference was deduced to the resistance effect of devices by analyzing the impedance spectra.2. Two novel narrow band gaped polymers of DTP-BTD and DTP-BH-BTD based on the Dithieno[3,2-b:2',3'-d]Pyrrole(DTP)were chosen to fabricate cells with the structures of ITO/PEDOT:PSS/DTP-BTD:PCBM/A1 and ITO/PEDOT:PSS/DTP-BH-BTD:PCBM/A1 together with the PCBM, respectively. The results showed that two polymers indeed extended the absorption active range to round 700nm; the external quantum efficiency (EQE) of cells also certified that the efficiency of cells showed the peak response at 450nm and 600nm. The extended absorption spectra of the active layer improved the ability of absorbing the photos and improve the performance of devices. The cells based on the DTP-BH-BTD showed much better photovoltaic performance:Jsc (3.16mA/cm2), Voe (0.4V), FF (0.44),ηwith the value of 0.51%.3. The photovoltaic properties of cells with the structure of ITO/PEDOT:PSS/F8T2: PCBM/Au after microwave annealing and common annealing oven respectively were compared. The results showed that the cell through microwave annealing(2.45GHZ,600W, 90s) showed better results:JSC(3.66mA/cm2), VOC(0.61V), FF (0.53),η(1.18%), theηwas higher as much as about 30% than the oven annealed one. The better performance of cells was deduced to the improvement of phase separation between F8T2 and PCBM, the orientation of polymer chains were occurred and provided the paths for the transform of carriers; In addition, the microwave not only can anneal active layer materials, but also can anneal metal electrode. The good ohmic contact between electrode and active layer was achieved after the microwave annealing.4. The single walled carbon nano tubes (SWCNTs) with good transmission and conductivity were chosen as anode, the photovoltaic properties of cells with structures of CNT/PEDOT:PSS/P3HT:PCBM/A1 and ITO/PEDOT:PSS/P3HT:PCBM/A1 was compared. When the annealing temperature and time were 150℃and 15min, the performance of cells based on CNT showed the best one:Jsc,VOC,FF,ηwas 4.01mA/cm2,0.614V,0.50,1.22%, respectively. The phenomenon of separation of thin film occurred in the experiment was studied, and several useful results and experience were also achieved.