| Summary: | 碩士 === 國立臺北科技大學 === 有機高分子研究所 === 99 === Polymer solar cells have gained wide interest in recent years, but how to further cut down the fabrication cost and increase the device lifetime is still an important issue for their commercialization. In this study, a series of assembled monolayers (SAMs) of benzoic acid with various para-substituted groups on ITO was employed to replace PEDOT:PSS as the electron blocking layer of polymer solar cells.
In the first part of this thesis, contact angle, X-ray photoelectron spectroscope, and AFM were applied to study the SAMs of benzoic acid derivatives on ITO. AFM images showed the presence of SAMs slightly reduced the surface roughness of ITO. In addition, the effect of SAMs on the work function of ITO was examined using AC-2. The experimental results indicated that the electron donating ability of the para-substituent on benzoic acid had decisive effect on the work function of ITO. An electron donating moiety will up-shift the work function but an electron withdrawing group will down-shift the work function of ITO. Finally, the SAMs-modified ITO was used as transparent anode to fabricate P3HT/PCBM bulk heterojunction solar cells. I-V measurements demonstrated that as the para-substituent was –CN or –CF3 group, the SAMs-based device reached a power conversion efficiency of 3.64%, which is comparable to that of a conventional solar cells with PEDOT:PSS as electron blocking layer.
In the second part, the SAMs-covered ITO which was patterned with ordered line-shaped groove was utilized as the anode of solar devices to shorten the transport pathway of hole. Preliminary results showed this patterned ITO is helpful in rising the short-circuit current. Further optimization on the thickness of photoactive layer and the dimension of groove is still undertaking by our group members.
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