You could place the labels yourself using text. Personally, I'd rather MATLAB figure out the placement.
Here's code which puts a set of invisible axes on top of the colorbar, turns the colorbar tick labels off, and instead shows labels for the axes ticks. The axes ticks are placed where labels previously existed in the colorbar. Then xtickangle rotates the labels.
figure;
[X,Y] = meshgrid(1:0.5:10,1:20);
Z = sin(X) + cos(Y);
offset = rand(1)*1e-6;
Z = Z*1e-14 + offset;
pcolor(X,Y,Z)
cmorig = colormap(gca);
view(2)
% changes/additions start here
cb = colorbar('southoutside');
keepLabels = ~cellfun(@isempty,cb.TickLabels);
cb.TickLabels = [];
ax = axes('Position', cb.Position,...
'Color', 'none',...
'YTick', [],...
'XLim', cb.Limits,...
'XTick', cb.Ticks(keepLabels),...
'FontSize', cb.FontSize);
xtickangle(ax, -30);
The result is this:
Of course repositioning the colorbar will mess it up. You may need to manually reposition some things yourself to keep the 'x 10^-n' within the figure.
This may be overcomplicated, but I wasn't sure how else to do it without placing the labels yourself. Hopefully this works for you!