Wannan takarda tana bincika takarda mai mahimmanci ta 1995 "Kwayoyin Photovoltaic na Polymer - Ingantattun Ayyuka ta Hanyar Cibiyar Sadarwar Donor-Acceptor na Ciki" wadda aka buga a cikin Kimiyya ta Yu, Hummelen, Wudl, da Heeger. Aikin yana wakiltar wani babban ci gaba a cikin photovoltaics na kwayoyin halitta (OPV), yana nuna cewa haɗa polymer mai ɗaukar wutar lantarki (donor) tare da masu karɓar fullerene (C60) zai iya inganta aikin canza makamashi fiye da sau biyu idan aka kwatanta da na'urorin da aka yi da polymer mai tsafta.
Babban ƙirƙira shine ƙirƙirar "cibiyar sadarwa mai ci gaba biyu" na cibiyoyin haɗin gwiwa na ciki a cikin wani fim ɗin haɗakar guda ɗaya, wanda ke ba da damar raba caji da tattara su yadda ya kamata—wani ra'ayi wanda ya zama tsarin ƙira na zamani na kwayoyin hasken rana na cibiyar haɗin gwiwa na gaba ɗaya (BHJ).
Binciken yana amfani da ƙa'idar canja wurin electron da hasken rana ya haifar daga wani abu mai ba da electron (D) zuwa wani abu mai karɓar electron (A). Bayan karɓar photon, ana haifar da wani exciton (haɗin electron-ramin da aka ɗaure) a cikin donor. Idan wannan exciton ya yadu zuwa wurin haɗuwa na D-A a cikin rayuwarsa, electron zai iya canzawa cikin sauri zuwa matakin LUMO na mai karɓa mafi ƙanƙanta, yana raba cajin yadda ya kamata.
An ƙirƙiri fina-finai ta hanyar haɗa waɗannan kayan daga wani magani na gama gari, wanda ya haifar da haɗakar fasalin.
Na'urorin photovoltaic suna da tsari mai sauƙi: an lulluɓe wani Layer mai aiki na haɗakar (MEH-PPV:C60 haɗakar) tsakanin electrodes guda biyu. Yawanci, ana amfani da anode na indium tin oxide (ITO) mai gani da cathode na ƙarfe (misali, Al, Ca/Al). Ma'aunin haɗakar da yanayin sarrafa fim sun kasance masu mahimmanci don samar da mafi kyawun cibiyar sadarwa mai shiga tsakani.
~29%
electrons kowace photon
~2.9%
ƙarƙashin hasken rana na kwaikwayo
> 100x
idan aka kwatanta da na'urorin MEH-PPV mai tsafta
Takarda ta ba da rahoton ma'auni guda biyu masu mahimmanci:
Bayanin Chati/Hoto (Dangane da Rubutu): Wani muhimmin chat a cikin takarda zai yi kama da yana nuna $\eta_e$ ko photocurrent akan yawan C60 a cikin haɗakar MEH-PPV. Bayanan za su nuna babban haɓaka—ta hanyar ma'auni—tare da ƙari na ko da 1% C60, sannan a kai kololuwa a mafi kyawun ma'aunin haɗakar (mai yiwuwa tsakanin 1:1 zuwa 1:4 ta nauyi). Bayan wannan mafi kyau, aikin zai ragu saboda rushewar hanyoyin jigilar caji. Wani muhimmin adadi zai kwatanta tsarin "cibiyar sadarwa mai ci gaba biyu" da aka tsara, yana nuna yankuna masu shiga tsakani na donor (polymer) da mai karɓa (fullerene) akan ma'auni na ~10-20 nm, wanda ya dace da tsawon yaduwar exciton.
Sakamakon ya tabbatar da cewa aikin quantum na raba caji ya kusanci haɗin kai, yayin da canja wurin electron na ƙasa-picosecond ya fi hanyoyin lalata exciton.
Hanyar asali ita ce canja wurin electron cikin sauri da hasken rana ya haifar. Bayan karɓar haske, MEH-PPV yana haifar da exciton. Idan wannan exciton ya kai wurin haɗuwa na D-A, electron yana canzawa zuwa matakin LUMO na C60, wanda yake da ƙarancin makamashi da kusan 0.5-1.0 eV. Wannan tsari, wanda ke faruwa a cikin <1 ps, an kwatanta shi da ka'idar canja wurin electron ta Marcus. Matsayin raba caji (MEH-PPV⁺/C60⁻) yana da tsayayye, yana hana sake haɗawa cikin sauri.
Bangaren juyin juya hali shine motsawa daga cibiyar haɗin gwiwa ta bilayer (tare da wurin haɗuwa na D-A na fili guda ɗaya) zuwa cibiyar haɗin gwiwa ta bulk. Haɗakar ta raba fasalin kai tsaye yayin samuwar fim, yana ƙirƙirar cibiyar sadarwa mai girma uku, mai shiga tsakani na donor da matakan mai karɓa. Wannan yana ƙara girman yankin D-A a cikin gaba ɗaya, yana tabbatar da cewa excitons da aka haifar da haske ba su taɓa zama fiye da tsawon yaduwa (~10 nm) daga wurin haɗuwa ba, ta haka yana magance matsalar matuƙar mahimmanci na gajerun tsayin yaduwar exciton a cikin semiconductors na kwayoyin halitta marasa tsari.
Aikin tantanin halitta na BHJ za a iya raba shi ta hanyar amfani da samfurin mai zuwa:
$$\eta_{e} = \eta_{A} \times \eta_{ED} \times \eta_{CT} \times \eta_{CC} \times \eta_{V}$$
Inda:
$\eta_{A}$ = Aikin ɗaukar Photon.
$\eta_{ED}$ = Aikin yaduwar Exciton zuwa wurin haɗuwa na D-A.
$\eta_{CT}$ = Aikin canja wurin caji a wurin haɗuwa (~1 a cikin wannan tsarin).
$\eta_{CC}$ = Aikin tattara caji a electrodes.
$\eta_{V}$ = Matsakaicin ƙarfin lantarki (mai alaƙa da matakan makamashi).
Gine-ginen BHJ yana inganta $\eta_{ED}$ kai tsaye ta hanyar samar da wuraren haɗuwa ko'ina kuma yana inganta $\eta_{CC}$ ta hanyar samar da hanyoyi masu ci gaba don ramuka (ta hanyar donor) da electrons (ta hanyar mai karɓa) zuwa nasu electrodes.
Yu da sauransu ba kawai sun gyara wani abu ba; sun sake fassara tsarin gine-gine don photovoltaics na kwayoyin halitta. Matsi daga wurin haɗuwa na fili zuwa cibiyar sadarwa mai girma uku, na nanoscale mai shiga tsakani ya kasance wani babban nasara wanda ya kai hari kai tsaye ga tushen toshewar semiconductors na kwayoyin halitta: gajerun tsayin yaduwar exciton mara kyau. Wannan shine lokacin "aha" wanda ya canza fagen daga sha'awar ilimi zuwa ƙalubalen injiniya mai yuwuwa.
Hankalin takarda ba shi da kyau: 1) Gano matsalar (sake haɗawa cikin sauri a cikin polymers masu tsafta). 2) Ba da shawarar maganin kwayoyin halitta (canja wurin electron da hasken rana ya haifar zuwa C60, wanda aka tabbatar a cikin aikin da ya gabata). 3) Gano matsalar matakin tsarin (ƙayyadaddun wurin haɗuwa a cikin bilayers). 4) Ƙirƙirar maganin matakin kayan aiki (haɗakar cibiyar haɗin gwiwa ta gaba ɗaya). 5) Tabbatar da ribar aikin ta hanyar ma'auni. Wannan misali ne na littafin karatu na binciken fassara, yana haɗa ilimin photophysics na asali zuwa injiniyan na'ura.
Ƙarfi: Bayyanannen ra'ayin BHJ shine babban ƙarfinsa. Aikin 2.9%, ko da yake ƙasa da ma'auni na yau (~18% don OPVs), ya kasance canji mai girman gaske wanda ya tabbatar da yuwuwar ra'ayin. Zaɓin C60 ya kasance mai wahayi, idan aka yi la'akari da kyawawan halayen karɓar electron, daga baya aka tabbatar da shi ta hanyar amfani da PCBM ([6,6]-Phenyl C61 butyric acid methyl ester), wani abu mai narkewa na C60 daga ƙungiyar bincike ɗaya.
Kurakurai & Mahallin: Idan aka duba ta hanyar tabarau na 2024, iyakokin takarda sun bayyana a sarari. Ba shi da cikakken siffanta yanayin (AFM, TEM) wanda daga baya ya zama daidaitaccen. Kwanciyar hankali na waɗannan na'urorin na farko mai yiwuwa ya kasance mara kyau—wani muhimmin aibi don kasuwanci wanda ba a magance shi ba. Aikin, ko da yake ya kasance mai ban mamaki, har yanzu yana nesa da kusan kashi 10% na bakin kofa da ake ɗauka a lokacin don ayyuka. Kamar yadda aka lura a cikin chat na NREL na rikodin ayyuka, OPVs sun ɗauki kusan shekaru 15 bayan wannan takarda don ci gaba da keta kashi 10%, yana nuna dogon, hanya mai wahala ta ingantawa wanda ya biyo bayan wannan fahimtar asali.
Ga masu bincike na zamani da kamfanoni: Yanayin yanayin shine sarki. Gadon wannan takarda shine mai da hankali sosai kan sarrafa rabon fasalin nanoscale na haɗakar. OPVs na zamani masu jagoranci suna amfani da ƙari masu haɗakar maganin ruwa, zafi mai zafi, da sabbin masu karɓa (kamar ITIC marasa fullerene) don cikar cibiyar sadarwar BHJ wanda Yu da sauransu suka fara tsara. Darasin shine cewa ra'ayin na'ura mai haske dole ne a haɗa shi da sarrafa kayan aiki mai kyau. Bugu da ƙari, gwagwarmayar fagen tare da kwanciyar hankali daga baya yana jaddada cewa aikin kadai shine ruɗi; tsawon rayuwar aiki shine ainihin ma'auni don yuwuwar kasuwanci. Duk wata ƙungiya da ke aiki akan PV na gaba dole ne ta ƙira don kwanciyar hankali tun daga ranar ɗaya, darasin da aka koya da wahala bayan wannan aikin majagaba.
Tsarin don Kimanta Sabon Kayan Aiki/Gine-ginen PV:
Wannan takarda a ɓoye tana kafa tsarin da har yanzu ake amfani da shi don kimanta sababbin ra'ayoyin PV:
Misalin Code na Ra'ayi (Pseudocode don Simulation na Aikin BHJ):
// Pseudo-code don sauƙaƙan simintin Monte Carlo na makomar exciton a cikin BHJ
initialize_3D_grid(blend_ratio, domain_size, exciton_diffusion_length)
generate_morphology() // Ƙirƙirar donor/acceptor phases
for each absorbed_photon:
exciton = create_exciton_at_random_location(donor_phase)
for step in range(max_diffusion_steps):
exciton.random_walk()
if exciton.position at donor_acceptor_interface:
if electron_transfer_probability() > random():
charge_separated_state = True
break // Nasara raba caji
if exciton.lifetime_exceeded():
exciton.recombines() // Hanyar asara
break
if charge_separated_state:
// Simulate charge transport to electrodes
if find_percolation_path_to_electrode(hole, donor_network) and
find_percolation_path_to_electrode(electron, acceptor_network):
collected_carriers += 1
calculated_efficiency = collected_carriers / total_photonsRa'ayin BHJ da aka fara a nan ya girma fiye da yadda ake buƙata a farkon mahallinsa. Hanyoyin yanzu da na gaba sun haɗa da: