The Fabrication Of Polymer Small Molecules Ternary Solar Cells And Their Photovoltaic Performance Research

The problems of world wide energy shortage and environment pollution are becoming more and more serious, thus lots of attention has been paid to renewable and sustainable energy. One of the most promising, clean energy sources is solar energy, which is clean, renewable, safe, ubiquitous. After years of study and exploration, solar cells have made tremendous progress in development. Bulk heterojunction(BHJ) organic solar cells(OSCs) have attracted intensively attention due to their potential in low-cost, light-weight, as well as large-area manufacturing processibility. Although the power conversion efficiency of the solution-processed PSCs have exceeded 10%, further development is required to ensure a bright industrial future for organic photovoltaics. Relatively narrow spectral overlap of organic polymer absorption bands within the solar spectrum is one of the major limitations of organic solar cells. The novel concept of ternary organic solar cells become a hot topic since the add of sensitizes can extend the absorption spectral range without negatively impact on the device parameters such as open circuit voltage.This paper took PTB7 as the donor material to study effects of addition of additives in blend active layer on device performance and the relations between device performance and the morphology of the active layer. Additionally, it described the characterization methods of several common active layer morphologies. Then, PTB7, DTS and PC71 BM were used to construct a ternary blend photovoltaic device, and 8.88% efficient device is obtained successfully. Furthermore, it studied the influence of DTS sensitizer material to the device performance and relation between corresponding active layer morphology and photovoltaic performance. It also searched the promotion cause of ternary device. Main works are as the following.In the second chapter, PTB7 was used as a donor material, and normal device structure was used to produce binary heterojunction cell. The device performance was optimized by adjusting the addition ratio of DIO. Several common methods on active layer morphologies were introduced from the perspective of test characterization, i.e. transmission electron microscopy(TEM), atomic force microscopy(AFM) and grazing incidence wide angle X-ray scattering(GIWAXS). These conclusions may provide references and comparison for following test on the effect of DTS to active layer morphologies.In the third chapter, p-DTS-(FBTTh2)2 was used as electron-cascade donor materials by incorporating it into organic photovoltaic cells prepared from a PTB7:PC71BM blend. The small molecules penetrated the PTB7:PC71BM blend layer to yield complementary absorption spectra through appropriate energy level alignment. A high short-circuit current(JSC) and fill factor(FF) are obtained using solar cells prepared with the ternary blend. The devices prepared from PTB7:DTS:PC71BM blend layer with 9:1(PTB7:DST by weight), 1% DIO have shown the best performance. The best device exhibit an PCE of 8.88% under AM 1.5G illumination(with a high intensity of 100 mW-2), with a JSC of 17.79 mA cm-2, an open circuit voltage(VOC) of 0.72 V and a FF of 69.38%. Compared with PTB7: PC71 BM binary device, the performance of ternary device was improved greatly.To explore the performance promotion cause of ternary device, a series of ternary devices with different DTS and DIO addition ratio were produced. With TEM,AFM and GIWAXS methods, the active layer morphologies were analyzed and taken comparison. Finally, it proved that the improvement of π-π stacking and crystallinity in the ternary system is the cause of short-circuit current and fill factor promotion.